Conventionally, an electric actuator may have a configuration including a worm gear, which is equipped directly to an output shaft of a motor to reduce its size. In the configuration, in which a worm gear is directly equipped to an output shaft of a motor, a thrust load is transmitted from a worm wheel. Thus, the thrust load is directly transmitted to the output shaft. Therefore, the output shaft is intensely urged with the thrust load in the axial direction. Therefore, the output shaft and the worm gear may be moved with the thrust load in the axial direction. In consideration of the present state, an additional configuration is needed to regulate movement of the output shaft and the worm gear.
For example, Patent Document 1 discloses a configuration in which a collar-shaped thrust support portion is equipped to a worm gear. The thrust support portion is greater than a thread of the worm gear in diameter. The thrust support portion is equipped with first and second thrust bearings on both sides in the axial direction to regulate movement of the output shaft and the worm gear. It is noted that, the configuration of the Patent Document 1 needs a special worm gear including the thrust support portion, in addition to the first and second thrust bearings. Accordingly, the configuration of Patent Document 1 may incur additional cost.
Alternatively, another configuration is conceivable in which, as shown in FIG. 4, a worm gear unit 101 is regulated from moving in the axial direction of to an other side. Specifically, the configuration of FIG. 4 enables a worm gear unit 101 to make contact with a bearing 103 of a motor 102 in the axial direction, thereby to regulate movement of the worm gear unit 101 toward the other side in the axial direction. It is noted that, movement of the worm gear unit 101 to the one side in the axial direction may be regulated with, for example, a regulating member 104. The regulating member 104 is a separate component from an electric actuator 100 and is fixed to the one side of the worm gear unit 101 in the axial direction.
It is noted that, in the configuration, the worm gear unit 101 makes contact with the bearing 103 to move the bearing 103 toward an armature coil 105. Consequently, a thrust clearance between the bearing 103 and the armature coil 105 may be eliminated to lock rotation of the motor 102. In consideration of this, it is further conceivable to provide a bearing retainer configuration, which retains the bearing 103 around the armature coil 105 in order not to enable the bearing 103 to move toward the armature coil 105. The bearing retainer configuration may be provided by, for example, crimping the yoke 106 and/or welding a separate component on the yoke 106. It is further noted that, the additional bearing retainer configuration may also incur additional cost.